1. Field of the Invention
The present invention relates to a system for the continuous monitoring of temperature and wear of a vehicle friction material. More specifically, the present invention relates to a system for the monitoring of temperature and wear of a vehicle friction material where an electrically resistive sensor is used to measure temperature and/or wear embedded in the brake lining.
2. Description of the Prior Art
The prior art is replete with devices to signal when a brake lining has worn to the extent where relining is necessary. U.S. Pat. Nos. 2,217,176; 2,814,684; 3,271,737; 3,297,985; 3,440,604; 3,553,642; 3,660,815 and 3,689,880 are examples of such systems, the disclosures of which are hereby incorporated by reference. All of these systems signal only when the brake lining wears to a predetermined thickness whereupon a signal is transmitted to indicate that service is required. U.S. Pat. No. 3,805,228 discloses a brake wear sensor where a plurality of preselected brake lining wear points are signaled by embedded sensors, each of which complete an electrical circuit when the lining wears to each predetermined thickness point.
Measuring brake temperature has been commonly accomplished by embedding a thermocouple into the brake lining. An example of such a method is shown in U.S. Pat. No. 3,674,114. The single function of the embedded thermocouple is to measure internal brake lining temperature with no wear monitoring capability.
Although the aforementioned prior art monitoring systems do give an indication of the state of the brake lining, none have proved satisfactory in the marketplace due to reliability problems, high cost, complication and performance limitations. These concepts are also susceptible to generating false signals due to contamination thereby triggering a premature servicing event. Most all the wear sensors only signal when the lining has worn to selected points without a continuous measurement capability and do not provide temperature sensing. Thus, using prior art techniques, two sensors are required to measure both lining wear and temperature.